Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device includes a substrate; an n-type transistor including a first junction region positioned on the substrate, a first channel region positioned on the first junction region, a second junction region positioned on the first channel region, and a first gate stack at least partially surrounding the first channel region; and a p-type transistor including a third junction region positioned on the substrate, a second channel region positioned on the third junction region, a fourth junction region positioned on the second channel region, and a second gate stack at least partially surrounding the second channel region, in which the first channel region and the second channel region are epitaxial channel layers.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent application Ser. No. 16/242,027, which is a divisional of U.S. patent application Ser. No. 15/655,196, filed Jul. 20, 2017, now U.S. Pat. No. 10,204,834, issued Feb. 12, 2019, which claims priority to and the benefit of Korean Patent Application No. 10-2016-0167936 filed in the Korean Intellectual Property Office on Dec. 9, 2016, the entire contents of which are incorporated herein by reference.

BACKGROUND Technical Field

The present inventive concepts relate to semiconductor devices and methods of manufacturing the same.

Description of Related Art

Semiconductor devices have characteristics, such as small size, multifunctionality, and/or low manufacturing cost, thereby being used in many electronic industries. The semiconductor device may include a memory device storing data, a logic element calculation-processing data, a hybrid element, which is capable of simultaneously performing various functions, and the like.

Due to the high development of the electronic industry, semiconductor devices may be highly integrated, so that semiconductor devices becomes small or fine, and various research has been conducted in order to integrate more devices, such as a transistor, within a limited area of a substrate. In order to decrease the area of the substrate occupied by one transistor, various transistor structures having a vertical semiconductor channel installed on a substrate have been suggested.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concepts and may contain information that does not constitute prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY

When a transistor having a vertical semiconductor channel is formed in order to allow higher device integration, a process of forming a junction may become more complex. The present inventive concepts provide semiconductor devices, of which process management is easier, and methods of manufacturing the same.

An example embodiment of the present inventive concepts provides a semiconductor device, including: a substrate; an n-type transistor including a first junction region positioned on the substrate, a first channel region positioned on the first junction region, a second junction region positioned on the first channel region, and a first gate stack at least partially surrounding the first channel region; and a p-type transistor including a third junction region positioned on the substrate, a second channel region positioned on the third junction region, a fourth junction region positioned on the second channel region, and a second gate stack at least partially surrounding the second channel region, in which the first channel region and the second channel region are epitaxial channel layers.

Another example embodiment of the present inventive concepts provides a method of manufacturing a semiconductor device, the method including: forming a first doping layer by implanting ions to an upper surface of a substrate; forming a first channel layer on the first doping layer by an epitaxy method; forming a second doping layer by implanting ions to an upper surface of the first channel layer; forming a first junction region, a first channel region, and a second junction region, which are sequentially positioned on the substrate, by etching the first doping layer, the first channel layer, and the second doping layer; and forming a first gate stack so as to at least partially surround the first channel region, in which the first doping layer and the second doping layer have the same conductivity type.

According to some example embodiments of the present inventive concepts, a method of fabricating a semiconductor device includes forming a first doped layer, an epitaxial channel layer, and a second doped layer sequentially stacked on a substrate; etching the second doped layer, the epitaxial channel layer, and the first doped layer to define a second junction region, a first channel region, and a first junction region, respectively; and forming a first gate stack on the first channel region between the first junction region and the second junction region responsive to the etching.

According to some example embodiments of the present inventive concepts, a method of fabricating a semiconductor device includes forming an n-type transistor on a substrate, the n-type transistor comprising a first junction region, a first channel region on the first junction region, and a second junction region on the first channel region; and forming a p-type transistor on the substrate adjacent the n-type transistor, the p-type transistor comprising a third junction region, a second channel region on the third junction region, and a fourth junction region on the second channel region. The first channel region and the second channel region are epitaxial layers.

According to example embodiments of the present inventive concepts, the lower junction region and the upper junction region are formed before the forming of the channel, so that it is possible to obtain a stable semiconductor device characteristic.

Further, the channel layer is formed by using a non-selective epitaxy process, so that it is possible to easily implement a collective process of a CMOS transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a transistor according to an example embodiment.

FIG. 2 is a cross-sectional view illustrating a CMOS transistor including the transistor of FIG. 1.

FIG. 3 is a cross-sectional view illustrating a modified CMOS transistor of the CMOS transistor of FIG. 2.

FIGS. 4 to 8 are cross-sectional views illustrating a method of manufacturing the transistor of FIG. 1.

FIGS. 9 to 13 are cross-sectional views illustrating a method of manufacturing the CMOS transistor of FIG. 2.

FIGS. 14 and 15 are cross-sectional views illustrating a method of manufacturing the CMOS transistor of FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, transistor structures in semiconductor devices according to example embodiments of the present inventive concepts will be described with reference to FIG. 1.

FIG. 1 is a cross-sectional view illustrating a transistor according to an example embodiment.

Referring to FIG. 1, a transistor according to an example embodiment includes a substrate 110, a lower junction region 120 positioned on the substrate 110, a channel region 130 positioned on the lower junction region 120, a gate stack 160 at least partially surrounding the channel region 130, and an upper junction region 140 positioned on the channel region 130.

The substrate 110 may include a semiconductor material, such as silicon, polysilicon, and germanium. In this case, the substrate 110 may be bulk silicon. Although not illustrated in FIG. 1, the substrate 110 may include a P-well region or an N-well region, or a silicon on insulator (SOI) structure.

In the lower junction region 120, n-type or p-type ions are doped in the same material as that of the substrate 110. When the lower junction region 120 is n-type, the lower junction region 120 may include a dopant, such as phosphorus (P), arsenic (As), and/or antimony (Sb), and when the lower junction region 120 is p-type, the lower junction region 120 may include boron (B) as a dopant.

The lower junction region 120 may include a first portion 120 x and a second portion 120 y having different thicknesses as illustrated in FIG. 1. The first portion 120 x is thicker than the second portion 120 y, and is a portion of the lower junction region 120 overlapping the channel region 130 and the upper junction region 140 in a vertical direction to the substrate 110. The second portion 120 y is a portion, which does not overlap the channel region 130 and the upper junction region 140. As used herein, the terms first, second, third, etc. are used merely to differentiate one region, portion, or element from another.

The transistor according to the present example embodiment may further include a spacer 150 positioned on the second portion 120 y of the lower junction region 120. The spacer 150 may overlap the second portion 120 y, and may have a height, which is the same as or larger than that of the first portion 120 x of the lower junction region 120, and may have a height, which is smaller than a height of the channel region 130. The spacer 150 may include an oxide, a silicon dioxide, a silicon nitride, and/or a silicon oxynitride. The spacer 150 may reduce or prevent an operation speed of the device from being decreased by a parasitic capacitor or parasitic capacitance.

The channel region 130 may include the same material as that of the substrate 110, and may be in a state of not being doped. The channel region 130 is formed by performing an epitaxy process. However, the channel region 130 may also include a dopant within a range in which a characteristic of the device is not influenced. For example, the range, in which a characteristic of the device is not influenced, may be a range, in which an on-off characteristic of the device is not influenced.

In the upper junction region 140, n-type or p-type ions are doped in the same material as that of the channel region 130. The dopant included in the upper junction region 140 has the same type as that of the dopant of the lower junction region 120. The upper junction region 140 may be disposed in a structure symmetric to the lower junction region 120 based on the channel region 130. In this case, a distance from the center portion of the channel region 130 to the upper junction region 140 may be substantially the same as a distance from the center portion of the channel region 130 to the lower junction region 120.

A distance between the lower junction region 120 and the upper junction region 140, that is, a thickness of the channel region 130, may be a length of the channel.

The gate stack 160 may have a shape at least partially surrounding the channel region 130 with the channel region 130 interposed therebetween. The gate stack 160 may include a gate dielectric layer and a gate conductor covering the gate dielectric layer. The gate dielectric layer may include a high dielectric material, an oxide, and/or a silicon dioxide. The gate conductor may be formed of a single conductive material, such as aluminum, copper, TiN, TaN, and TaC, or by combining the conductive materials.

A contact auxiliary layer 145 may be positioned on the upper junction region 140. The contact auxiliary layer 145 may be formed by an epitaxy process. In this case, when the epitaxy process is performed, a material is grown in a horizontal direction, as well as a vertical direction to the upper junction region 140, so that a width of the contact auxiliary layer 145 may be larger than that of the upper junction region 140. When the contact auxiliary layer 145 is formed, an area of a contact with a contact plug, which is to be described below, may be increased, thereby decreasing resistance.

A dielectric region 165 is positioned on the substrate 110, the lower junction region 120, the channel region 130, the upper junction region 140, and the spacer 150 while having a contact hole. The contact hole of the dielectric region 165 includes a lower contact plug 170, an upper contact plug 180, and a gate contact plug (not illustrated), which are in contact with the lower junction region 120, the upper junction region 140, and the gate stack 160, respectively. The contact auxiliary layer 145 is positioned between the upper junction region 140 and the upper contact plug 180, so that the upper contact plug 180 may be substantially in contact with the contact auxiliary layer 145. The lower contact plug 170, the upper contact plug 180, and the gate contact plug may be formed of a conductive material, and the gate contact plug (not illustrated) may be connected to a lateral surface of the gate stack 160. However, the present inventive concepts are not limited thereto. For example, a lateral portion of the gate stack 160 may be formed to protrude to a region, which does not overlap in the vertical direction to the upper contact plug 180 and the substrate 110, so that the gate contact plug may also be connected to an upper surface of the gate stack 160.

In the present example embodiment, the lower junction region 120 and the upper junction region 140 are formed by an ion implantation process, which will be described below, so that there are little limitations of a dopant compared to the case where the lower junction region 120 and the upper junction region 140 are formed by an epitaxy process. Particularly, in a situation where only the technology using phosphorus (P) as a dopant in order to form the junction region by the epitaxy process, has been developed, when the junction region is formed by the ion implantation like the present example embodiment, arsenic (As) and antimony (Sb) may also be used as the dopant, as well as phosphorous (P). When the relatively light phosphorous (P) is used as the dopant, the dopant may be dispersed to the channel region 130 during the heat process, but like the present example embodiment, when arsenic (As) or antimony (Sb) is used as the dopant, the aforementioned dispersion may be decreased.

FIG. 2 is a cross-sectional view illustrating a CMOS transistor including the transistor of FIG. 1. Particularly, FIG. 2 represents a CMOS transistor, in which the transistor described with reference to FIG. 1 is formed of an n-type transistor and a p-type transistor.

Referring to FIG. 2, the CMOS transistor according to the present example embodiment includes an n-type transistor 100 a and a p-type transistor 100 b.

The n-type transistor 100 a includes a P-well region 115 a positioned on the substrate a first junction region 120 a positioned on the P-well region 115 a, a first contact plug 170 a contacting the first junction region 120 a, a first channel region 130 a positioned on the first junction region 120 a, a first gate stack 160 a at least partially surrounding the first channel region 130 a, a second junction region 140 a positioned on the first channel region 130 a, a first contact auxiliary layer 145 a positioned on the second junction region 140 a, and a second contact plug 180 a contacting the first contact auxiliary layer 145 a. The first junction region 120 a and the second junction region 140 a may include an n-type dopant.

Although not illustrated, the CMOS transistor according to the present example embodiment may further include a gate contact plug connected with the first gate stack 160 a and a gate contact plug connected with the second gate stack 160 b.

The p-type transistor 100 b includes an N-well region 115 b positioned on the substrate 110, a third junction region 120 b positioned on the N-well region 115 b, a third contact plug 170 b contacting the third junction region 120 b, a second channel region 130 b positioned on the third junction region 120 b, a second gate stack 160 b at least partially surrounding the second channel region 130 b, a fourth junction region 140 b positioned on the second channel region 130 b, a second contact auxiliary layer 145 b positioned on the fourth junction region 140 b, and a fourth contact plug 180 b contacting the second contact auxiliary layer 145 b. The third junction region 120 b and the fourth junction region 140 b may include a p-type dopant.

A device isolating region 113 is formed in order to isolate the n-type transistor 100 a and the p-type transistor 100 b. The device isolating region 113 may be formed of an oxide layer, and may (for example) be formed of silicon dioxide. The device isolating region 113 may (for example) be formed by a shallow trench isolation (STI) process or a local oxidation of silicon (LOCOS) process. The device isolating region 113 may insulate the n-type transistor 100 a and the p-type transistor 100 b in order to reduce or prevent undesired leakage current from flowing between the n-type transistor 100 a and the p-type transistor 100 b.

In the present example embodiment, both the first channel region 130 a and the second channel region 130 b are epitaxial channel layers. The first junction region 120 a may include a first portion and a second portion having a smaller thickness than that of the first portion, and the third junction region 120 b may include a third portion and a fourth portion having a smaller thickness than that of the third portion.

FIG. 3 is a cross-sectional view illustrating a modified CMOS transistor of the CMOS transistor of FIG. 2.

In the example embodiment of FIG. 3, the CMOS transistor is mostly the same as the CMOS transistor described with reference to FIG. 2, and different parts or elements will be described in greater detail below.

Referring to FIG. 3, the P-well region 115 a and the N-well region 115 b included in the CMOS transistor according to the example embodiment of FIG. 2 are not provided, and a silicon on insulator (SOI) structure is provided instead, so that an oxide layer 112 is formed on the substrate 110 in a form of a thin film. The SOI structure can be used to decrease a burden of a process forming the well region in consideration of scaling, and when the SOI structure is used, a pnpn junction structure is not made, so that it is possible to reduce or prevent a latchup phenomenon, in which a current excessively flows and is burned.

FIGS. 4 to 8 are cross-sectional views illustrating a method of manufacturing the transistor of FIG. 1.

Referring to FIG. 4, a lower doping layer 120 p is formed by injecting ions to an upper surface of a substrate 110. N-type or p-type ions may be doped in the lower doping layer 120 p, and when a lower junction region, which is subsequently formed, is the n-type, the lower doping layer 120 p may include a dopant, such as phosphorous (P), arsenic (As), and antimony (Sb), and when the lower junction region is the p-type, the lower doping layer 120 p may include boron (B) as a dopant. Doping layers as described herein may also be referred to as doped layers.

Next, an annealing process may be performed. A defect may be generated inside crystals of the substrate 110 during the ion implantation process, and the defect may be decreased through the annealing process.

Referring to FIG. 5, a channel layer 130 p is formed on the lower doping layer 120 p by performing an epitaxy process with the same material as that of the substrate 110. The channel layer 130 p may be in a non-doped state, but the channel layer 130 p may also include a dopant within a range, in which a characteristic of a device is not influenced. A non-selective epitaxy process may be applied to the channel layer 130 p, and the non-selective epitaxy process does not refer to the forming of the channel layer 130 p on only a part of the upper surface of the substrate 110, but may refer to the forming of the channel layer 130 p on an entire surface of the substrate 110.

Referring to FIG. 6, an upper doping layer 140 p is formed by implanting ions to an upper surface of the channel layer 130 p. N-type or p-type ions may be doped in the upper doping layer 140 p, and the dopant included in the upper doping layer 140 p has the same type as that of the dopant of the lower doping layer 120 p.

Next, the annealing process may be performed. A defect may be generated inside crystals of the channel layer 130 p during the ion implantation process, and the defect may be decreased through the annealing process.

Referring to FIGS. 6 and 7, a lower junction region 120, a channel region 130, and an upper junction region 140, which are sequentially positioned on the substrate 110, are formed by etching the lower doping layer 120 p, the channel layer 130 p, and the upper doping layer 140 p. In this case, a part of the lower doping layer 120 p, which does not overlap the channel region 130, is etched, so that the lower junction region 120 may be formed to include a first portion 120 x and a second portion 120 y, which have different thicknesses. The first portion 120 x is thicker than the second portion 120 y, and is a portion overlapping the channel region 130 and the upper junction region 140.

The second portion 120 y is a portion, which does not overlap the channel region 130 and the upper junction region 140.

In FIG. 7, a spacer 150 may be formed on the second portion 120 y. In this case, a height of the spacer 150 may be the same as or larger than a height of the first portion 120 x of the lower junction region 120, and may be smaller than a height of the channel region 130.

Referring to FIG. 8, a gate stack 160 is formed so as to at least partially surround the channel region 130. The gate stack 160 may include a gate dielectric film and a gate conductor on or covering the gate dielectric film. The gate dielectric layer may include a high dielectric material, an oxide, and/or a silicon dioxide. The gate conductor may be formed of a single conductive material, such as aluminum, copper, TiN, TaN, and TaC, or by combining the conductive materials.

Then, a dielectric region having contact holes, which are in contact with the lower junction region 120, the upper junction region 140, and the gate stack 160, respectively, is formed, and then, a lower contact plug 170 and an upper contact plug 180 which are illustrated in FIG. 1, and a gate contact plug (not illustrated) may be formed by filling a conductive material.

In some conventional devices, a transistor having a vertical semiconductor channel may be formed by first forming a channel and then forming a lower junction region and an upper junction region. However, in this case, the lower junction region may be formed in or by using a narrow space between previously formed channels, a gate stack may be formed, and then the upper junction region may be formed, but a depth of the junction region may depend on control of a height of the gate stack, so that a process variation may be large. Accordingly, a general process management may be difficult, so that there may be difficulty in the collective process development of the CMOS transistor. However, in the present example embodiments, the junction region is formed by using the ion implantation process and the non-selective epitaxy process is applied, so that the collective process development of the CMOS transistor is easy, and a defect generation region, which may be generated in a border of a region of each device, may be reduced or minimized by decreasing the amount of epitaxy process, thereby being advantageous to decrease a size of the device.

FIGS. 9 to 13 are cross-sectional views illustrating a method of manufacturing the CMOS transistor of FIG. 2.

Referring to FIG. 9, a device isolating region 113 is formed on a substrate 110 by performing a device isolating process. In the present example embodiment, the device isolating region 113 may be formed by a shallow trench isolation (STI) process or a local oxidation of silicon (LOCOS) process.

Referring to FIG. 10, a P-well region 115 a and an N-well region 115 b are formed in the substrate 110, and a first doping layer 120 ap and a third doping layer 120 bp are formed by implanting ions to the P-well region 115 a and the N-well region 115 b, respectively. In this case, the first doping layer 120 ap may be doped with n-type ions, and phosphorous (P), arsenic (As), and/or antimony (Sb) may be included as an n-type dopant. The third doping layer 120 b p may be doped with p-type ions, and boron (B) may be included as a p-type dopant.

Referring to FIG. 11, a channel layer 130 p is formed on the first doping layer 120 ap, the device isolating region 113, and the third doping layer 120 bp by performing an epitaxy process with the same material as that of the substrate 110. Since the non-selective epitaxy process is applied to the channel layer 130 p, the channel layer 130 p may be formed on both an n-type region and a p-type region.

Then, a second doping layer 140 ap and a fourth doping layer 140 bp are formed by implanting ions to an upper surface of the channel layer 130 p overlapping the first doping layer 120 ap and the third doping layer 120 bp, respectively. In this case, a dopant included in the second doping layer 140 ap has the same type as that of the first doping layer 120 ap, and a dopant included in the fourth doping layer 140 bp has the same type as that of the third doping layer 120 bp.

Referring to FIGS. 11 and 12, a first junction region 120 a, a first channel region 130 a, and a second junction region 140 a, which are sequentially positioned on the substrate 110, are formed by etching the first doping layer 120 ap, the channel layer 130 p, and the second doping layer 140 ap, and a third junction region 120 b, a second channel region 130 b, and a fourth junction region 140 b, which are sequentially positioned on the substrate 110, are formed by etching the third doping layer 120 bp, the channel layer 130 p, and the fourth doping layer 140 bp. In this case, a part of the first doping layer 120 ap, which does not overlap the first channel region 130 a, is etched and a part of the third doping layer 120 b p, which does not overlap the second channel region 130 b, is etched, so that the first junction region 120 a may include a first portion and a second portion, which have different thicknesses, the second portion having a smaller thickness than that of the first portion, and the third junction region 120 b may include a third portion and a fourth portion, which have different thicknesses, the fourth portion having a smaller thickness than that of the third portion.

Then, a spacer 150 is formed on the second portions of the first junction region 120 a and the third junction region 120 b.

Referring to FIG. 13, a first gate stack 160 a is formed so as to at least partially surround the first channel region 130 a and a second gate stack 160 b is formed so as to at least partially surround the second channel region 130 b. Each of the first and second gate stacks 160 a and 160 b may include a gate dielectric layer and a gate conductor covering the gate dielectric layer.

Then, a first contact plug 170 a, a second contact plug 180 a, a third contact plug 170 b, and a fourth contact plug 180 b illustrated in FIG. 2 may be formed by forming a dielectric region having contact holes for contacting the first junction region 120 a, a first contact auxiliary layer 145 a formed on the second junction region 140 a by an epitaxy process, the third junction region 120 b, and a second contact auxiliary layer 145 b formed on the fourth junction region 140 b by an epitaxy process, and then filling the contact holes with a conductive material.

In the present example embodiment, the isolating process for electrically insulating the devices is performed before the epitaxy process, so that it is possible to decrease difficulty in the isolating process and address a limitation of a heat process that may be required when the isolating process is performed after the forming of the channel, thereby obtaining a stable device characteristic and isolation characteristic.

FIGS. 14 and 15 are cross-sectional views illustrating a method of manufacturing the CMOS transistor of FIG. 3.

In the example embodiment of FIGS. 14 and 15, a method of manufacturing the CMOS transistor is mostly the same as the method of manufacturing the CMOS transistor described with reference to FIGS. 9 to 13, and different parts or elements will be described in greater detail below.

Referring to FIG. 14, an oxide layer 112 is formed between a substrate 110 and a silicon single crystal layer 116 in a form of a thin film by applying a silicon on insulator (SOI) process. Then, a device isolating region 113 is formed by performing a device isolating process, and referring to FIG. 15, a first doping layer 120 ap and a third doping layer 120 bp are formed by implanting ions to the silicon single crystal layer 116.

In the present example embodiment, the operations of forming the P-well region 115 a and the N-well region 115 b in the method of manufacturing the CMOS transistor described with reference to FIGS. 9 to 13 are not included, and the SOI process is performed instead so that the oxide layer 112 is formed between the substrate 110 and the silicon single crystal layer 116.

Then, when the processes described with reference to FIGS. 11 to 13 are performed in the same way, it is possible to manufacture the CMOS transistor illustrated in FIG. 3.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. It will be understood that when an element is referred to as being “on” or “connected to” or “adjacent” another element (e.g., a layer or substrate), it can be directly on or connected to or adjacent the other element, or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or “directly connected to” or “immediately adjacent” another element, there are no intervening elements present.

It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the scope of the present inventive concepts.

It will be understood that spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The use of the terms “a” and “an” and “the” and similar references herein are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “and/or” includes any and all combinations of one or more of the associated listed items.

While the inventive concepts have been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the inventive concepts are not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

What is claimed is:
 1. A semiconductor device, comprising: a substrate; a first transistor comprising a first doped region on the substrate, a first channel region on the first doped region, a first pattern comprising a second doped region on the first channel region and a first epitaxial layer on the second doped region, and a first gate stack surrounding at least a portion of the first channel region; and a first contact plug on the first transistor, wherein the first contact plug overlaps an upper surface of the first epitaxial layer and side surfaces of the first epitaxial layer, and wherein the side surfaces of the first epitaxial layer directly contact the first contact plug.
 2. The semiconductor device of claim 1, wherein a width of the first epitaxial layer is greater than a width of the second doped region.
 3. The semiconductor device of claim 1, wherein a width of the first contact plug is greater than a width of the second doped region.
 4. The semiconductor device of claim 1, further comprising: a first spacer on the first doped region; and an interlayer insulating layer on the first spacer, wherein the first doped region comprises a first portion overlapping the first channel region and a second portion overlapping the first spacer in a vertical direction perpendicular to an upper surface of the substrate, and wherein a thickness of the first portion of the first doped region is greater than a thickness of the second portion of the first doped region.
 5. The semiconductor device of claim 1, further comprising: a first spacer on the first doped region, wherein at least a portion of the first gate stack is at a level higher than an upper surface of the first spacer, and wherein a bottom surface of the first gate stack is in contact with the first spacer.
 6. The semiconductor device of claim 1, further comprising: a second transistor comprising a third doped region on the substrate, a second channel region on the third doped region, a second pattern comprising a fourth doped region on the second channel region and a second epitaxial layer on the fourth doped region, and a second gate stack at least partially surrounding the second channel region; and a second contact plug on the second transistor, wherein the second contact plug overlaps an upper surface of the second epitaxial layer and side surfaces of the second epitaxial layer.
 7. The semiconductor device of claim 6, wherein a width of the second epitaxial layer is greater than a width of the fourth doped region.
 8. The semiconductor device of claim 6, further comprising: a P well region between the substrate and the first doped region; and an N well region between the substrate and the third doped region.
 9. The semiconductor device of claim 6, further comprising: an insulation layer that is between the substrate and the first doped region and between the substrate and the third doped region.
 10. A semiconductor device, comprising: a substrate; a first transistor comprising a first doped region on the substrate, a first channel region on the first doped region, a second doped region on the first channel region, and a first gate stack surrounding at least a portion of the first channel region; a first contact plug on the second doped region; a first spacer on the first doped region; and an isolation region on an edge sidewall of the first doped region and in contact with the first spacer, wherein an upper surface of the isolation region is at a level higher than a lower surface of the first spacer.
 11. The semiconductor device of claim 10, further comprising: a second contact plug penetrating the first spacer and electrically connecting the first doped region, wherein the upper surface of the isolation region is at a level higher than a lower surface of the second contact plug.
 12. The semiconductor device of claim 11, further comprising: a second transistor comprising a third doped region on the substrate, a second channel region on the third doped region, a fourth doped region on the second channel region, and a second gate stack surrounding at least a portion of the second channel region in a plan view; a third contact plug on the fourth doped region; and a second spacer on the third doped region.
 13. The semiconductor device of claim 12, further comprising: a fourth contact plug penetrating the second spacer and electrically connecting the third doped region, wherein the upper surface of the isolation region is at a level higher than a lower surface of the fourth contact plug.
 14. The semiconductor device of claim 12, wherein the isolation region is between the first doped region and the third doped region.
 15. The semiconductor device of claim 10, wherein the first doped region comprises a first portion overlapping the first channel region and a second portion overlapping the first spacer in a vertical direction perpendicular to an upper surface of the substrate, and wherein a thickness of the first portion of the first doped region is greater than a thickness of the second portion of the first doped region.
 16. The semiconductor device of claim 10, wherein at least a portion of the first gate stack is at a level higher than an upper surface of the first spacer, and wherein a bottom surface of the first gate stack is in contact with the first spacer.
 17. A semiconductor device, comprising: a substrate; a first doped region on the substrate; a first channel region on the first doped region; a second doped region on the first channel region; a first gate stack surrounding at least a portion of the first channel region; a first contact auxiliary layer on the second doped region and having a width greater than a width of the second doped region; a first contact plug contacting the first contact auxiliary layer; a second contact plug contacting the first doped region; a third doped region on the substrate; a second channel region on the third doped region; a fourth doped region on the second channel region; a second gate stack surrounding at least a portion of the second channel region in a plan view; a second contact auxiliary layer on the fourth doped region and having a width greater than a width of the fourth doped region; a third contact plug contacting the second contact auxiliary layer; a fourth contact plug contacting the third doped region; and an isolation region between the first doped region and the third doped region.
 18. The semiconductor device of claim 17, further comprising: a P well region between the substrate and the first doped region; and an N well region between the substrate and the third doped region.
 19. The semiconductor device of claim 17, further comprising: an insulation layer that is between the substrate and the first doped region and between the substrate and the third doped region, wherein a lower surface of the isolation region contacts the insulation layer. 